New Technology Enables Development of Field in Norwegian Sea

The ærfugl field is a gas condensate field located in the Norwegian Sea to the West of Skarv and Idun fields. The first phase consisting of well 4, 5 and 6 is planned to be developed with three off single slot templates as a 20 km long tie-back to the Aker BP operated Skarv FPSO connected to existing subsea infrastructure. The field layout can be seen in Heat input into the flow line system is required during shut down and potentially also during off-plateau production periods. A new enabling technology Electrically Heat Traced Flowline (EHTF) will be utilised to enable system start-up and shut down, and to maintain the production fluids outside of the hydrate envelope during steady state operation. The EHTF system is developed by Subsea 7 and ITP InTerPipe. The ærfugl EHTF system consists of an electrically heated 10" flowline inside a 16" carrier pipe (Pipe in Pipe). The large annulus between the 10" and the 16" allows for good insulation, and combined with reduced annulus pressure, a U-value of less than 0.5 W/m/K is achieved. Such a low U-value allows for a more passive system where only limited power is required for heating. The ærfugl EHTF system is based on a topside transformer. The power cables go directly from a topside bus bar via a dynamic and static power umbilical system to the In-Line Power Inlet Structure (ILPISTM) on the Electrically Heat Traced Flowline (EHTF). There is as such not any sophisticated subsea components to transform or split the current. All components that may need maintenance and repair are located topside. This gives a high availability and reliability of the subsea system. The EHTF technology is new. As such, we have limited literature on this technology. The paper will present how the EHTF technology works, and describes how it is set up for the ærfugl field. The information provided in this paper can be used as input to evaluate if EHTF should be considered in developments of new fields. This is especially relevant for fields with challenging flow assurance, such as long tie-backs.